The present invention concerns a decorated key top of beautiful appearance giving a feeling of high quality that can be manufactured at low cost, such as push buttons, used for cellular phones, portable information terminals, remote controls for various home electric appliances, card remote controls and various keyboards.
As a method for decorating with metallic gloss or pearl gloss the key top portion as a push button, used for a conventional cellular phone, a portable information terminal, a remote control for various home electric appliances, a card remote control and various keyboards or the like, a molding method by blending resin or rubber composing the key top with metal powder or pearl pigment, a screen printing or spraying method of paint containing metal powder or pearl pigment, a metal film deposition method of aluminum, chrome, or the like by evaporation of metal plating, are known.
Moreover, recently, a key top of beautiful appearance giving a feeling of high quality, having light transparent rainbow-colored gloss is strongly demanded.
However, the molding method by blending resin or rubber composing the key top with metal powder or pearl pigment produces a striped pattern or uneven color tone due to powder segregation, as it is difficult to disperse powder uniformly, can not obtain an uniform gloss of good feel of material, causing problems from aesthetic point of view.
Also, the printing or spraying method of paint containing metal powder or pearl pigment could not obtain a decorated key top having an even rainbow-colored gloss of good feel of material.
Further, a key top wherein aluminum or chrome or other metal film is deposited by evaporation or metal plating presents an even metallic gloss, but is lacking the rainbow-colored gloss.
On the other hand, methods by the Applicant, described in Japanese Patent Laid-Open HEI 10-289633 and Japanese Patent Laid-Open HEI 11-176273, provide a decorated key top reflecting selectively light of a particular frequency and having a rainbow-colored gloss, by laminating, in any film thickness, films of inorganic matter such as titanium oxide, but they were inappropriate for mass production because of batch film deposition operation taking much processing time. Moreover, film deposition requires complicated jigs and provokes other problems. Further, as these methods use inorganic matter, compounding with the key top made of organic polymer material, often required various adulteration treatments, increasing labor and cost.
The present invention provides a decorated key top having a selective reflection wavelength band in the visible light range, presenting a light transmitting rainbow-colored gloss and a beautiful appearance giving a feeling of high quality, that can be produced at low cost, by providing the key top surface and/or back with a cholesteric orientation liquid crystalline organic polymer layer, to solve said problem.
The selection of a liquid crystalline organic polymer layer wherein the reflective wavelength is visible light, violet, blue, green, yellow, red or other color tones can be obtained, and reflected light reinforcing wavelength allows the color tone to be controlled.
Namely, it is a decorated key top, wherein a liquid crystalline organic polymer layer having a selective reflection wavelength band in the visible light is formed on the key top surface and/or back.
Moreover, it is a decorated key top, wherein a liquid crystalline organic polymer layer having a selective reflection wavelength band in the visible light is formed, through a plastic film, on the key top surface and/or back.
Further, it is a decorated key top, wherein the liquid crystalline organic polymer layer is composed of cholesteric orientation liquid crystalline organic polymer. Moreover the invention relates to a manufacturing method of decorated a key top, wherein a liquid crystalline organic polymer layer having a selective reflection wavelength band in the visible light is formed on the surface and/or back of a key top molded by a die, or on the surface of a key top formed by dripping liquid resin on a base of polymer material, reacting and hardening the same, through application of crystalline organic polymer and then cholesteric orientation.
Further, the invention relates to a manufacturing method of a decorated key top, wherein a liquid crystalline organic polymer layer having a selective reflection wavelength band in the visible light is formed on the surface and/or back of a key top molded by a die, or on the surface of a key top formed by dripping liquid resin on a base of the polymer material, reacting and hardening the same, by gluing a plastic film having cholesteric orientated crystalline organic polymer layer.
Further, the invention relates to a manufacturing method of a decorated key top, wherein a liquid crystalline organic polymer layer having a selective reflection wavelength band in the visible light is formed on the surface and/or back of a key top molded by a die, or on the surface of a key top formed by dripping liquid resin on a base of polymer material, reacting and hardening the same, by placing a heat transfer sheet having cholesteric orientated crystalline organic polymer layer, and transferring the same by heat and pressure.
As the liquid crystalline organic polymer of the present invention, all of those that are in a crystal state at and beyond the glass transition point and in a glass state at and below the glass transition point can be used, and for example, backbone type liquid crystalline organic polymers such as polyester, polyamide, polyester amid, polycarbonate, polyester imide, polyether, polythiol or the like, polyacrylate base, polymethaacrylate base, polysiloxane base or polymalonate base side-chain type liquid crystalline organic, polymers, rod form stiff backbone type liquid crystalline organic polymers such as synthetic polypeptide, cellulose derivatives, polyisocyanate or the like, and their composite liquid crystalline organic polymers can be used.
The liquid crystalline organic polymer layer is required to be orientated in order to present a rainbow-colored gloss, and such orientation includes smectic orientation, nematic orientation, cholesteric orientation, discotic orientation, but cholesteric orientation and discotic orientation are preferable, and from the viewpoint of color, gloss, handling, or the like, cholesteric orientation is most preferable.
Now, the present invention will be described more in detail.
The liquid crystalline organic polymer layer of the present invention is preferably a multi-layer structure wherein layers of mono-domain having anisotropy in the molecular orientation are superposed continuously in a helical form. The central wavelength of light selectively reflected by the obtained decorated key top depends on the film thickness of a single layer. The film thickness of a single layer is preferably 50 nm 300 nm, and further, considering the optical selective reflection at the specific wavelength, the number of layers is preferably 5 to 50, and the total thickness is preferably 250 nm to 15000 nm. If the total thickness is less than 250 nm, the rainbow-colored gloss becomes pale, and if it exceeds 15000 nm, the translucency decreases disadvantageously.
In practice, though it is subjected to the nature, refractive index, shape of polymer material used for the key top and to the material, refractive index, color tone or the like of liquid crystal polymer, a total thickness range of 500 nm to 5000 nm presents a high optical selective reflection at tie specific wavelength. A beautiful key top presenting rainbow-colored gloss, mainly in red, yellow, blue or violet, that could not be obtained conventionally, can be obtained.
In addition, in order to recognize characters and symbols printed under the liquid crystalline organic polymer layer, it is undesirable that the total light beam transmittance of the liquid crystalline organic polymer layer is less than 70%, because the translucency becomes insufficient. The preferable total light beam transmissibility is equal or superior to 75%, and more preferably, equal or superior to 80%. Note that the total light beam transmittance used for the present invention is a value based on JIS (Japanese Industrial Standard) K7105.
The cholesteric orientation liquid crystalline organic polymer layer having its selective reflection wavelength band in the visible light can be prepared by known methods (1) to (4) described below. Especially, a liquid crystalline organic polymer layer having its selective reflection wavelength band in the visible light obtained by the methods (2) or (3) have a beautiful appearance, a good productivity and are, therefore, preferable.
(1) Method wherein low molecular liquid crystal is cholesteric oriented, and then cross-linked by optical reaction or thermal reaction or the like to fix the orientation.
(2) Method wherein side-chain type or backbone type thermotropic polymer liquid crystal is cholesteric orientated in liquid crystal state, and then cooled to a temperature equal or inferior to the liquid transition point, to fix the orientation state.
(3) Method wherein side-chain type or backbone type lyotropic polymer liquid crystal is cholesteric orientated in liquid crystal state, and then the orientation state is fixed by progressively removing medium.
(4) Cholesteric orientation liquid crystalline organic polymer obtained by the method (1) to
(3) is ground to fine powder, blended with painting resin or printing ink or the like, to paint or print the same.
In order to form a liquid crystalline organic polymer layer on the recto/verso of a key top, liquid crystalline organic polymer is applied directly over the key top, or after having disposed base coat layer and exerting rubbing treatment or the like over the surface thereof, the cholesteric orientation structure is formed, and fixed without damaging the orientation in the liquid crystal state. This provides a decorated key top provided with liquid crystalline organic polymer layer.
On the other hand, in order to form a liquid crystalline organic polymer layer on a plastic film, the orientation function is afforded to the plastic film by rubbing treatment or the like, a liquid crystalline organic polymer is applied, and then the cholesteric orientation structure is formed, and fixed without damaging the orientation in the liquid crystal state. This provides a decorated key top provided with a liquid crystalline organic polymer layer, and thus a film wherein a cholesteric orientation liquid crystalline organic polymer layer is formed. A decorated key top provided with a liquid crystalline organic polymer layer is obtained by gluing this film to the key top.
Additionally, in order to form a liquid crystalline organic polymer layer on a heat transfer film, the orientation function is afforded by Tubbing treatment or the like to a thin plastic film on which a detachment layer is provided and further a protective layer is provided to smooth the surface thereof, liquid crystalline organic polymer is applied to this film, and then the cholesteric orientation structure is formed, and fixed without damaging the orientation in the liquid crystal state to form a cholesteric orientation liquid crystalline organic polymer layer, and further, a hot melt adhesive layer is applied thereto, to prepare a heat transfer sheet of liquid crystalline organic polymer layer. This heat transfer sheet is opposed to the surface and/or back of the key top, and transferred by applying beat and pressure by a known heat transfer method, to obtain a decorated key top provided with a liquid crystalline organic polymer layer. Here, a protective layer maybe disposed between the liquid crystalline organic polymer and the hot melt adhesive layer in order to protect the liquid crystalline organic polymer layer.
Concerning the method to afford the key top or film of the present invention with orientation function, in addition to the rubbing treatment, the orientation function can be afforded by using a known film or by rubbing directly in one direction with a piece of cloth. As for the method to apply liquid crystalline organic polymer, screen printing, tampo printing, photogravure, flexography, or other printing methods, or application, dipping, potting or the like may be used without special restriction.
Further, different reflective color tone points can be formed by varying selectively reflecting light wavelength through the orientation treatment under the different cooling conditions by scanning a desired point of the liquid crystalline organic polymer layer with YAG laser beam and heat melting the liquid crystalline organic polymer layer of that point, or it is possible to obtain a color tone wherein the specific wavelength selective reflectivity is cancelled partially or totally, by changing an an-isotropic layer of the oriented liquid crystal to an isotropic layer through the high power YAG laser beam scanning. Similarly, portions of any form such as characters, symbols or the like without cholesteric reflective color can be obtained by burning and removing desired points through the high power YAG laser beam scanning. The material of the key top of the present invention includes all key tops made of resin or rubber elastic element.
Though the composition, nature, elasticity or color tone of resins used for the key top are not specially specified, it is preferable that their translucency is good, and more particularly, poly methyl methacrylate, polyearbonate, silicone resin, amorphous polyester, PVC, polystyrene, polyacrylate, amorphous polyolefin, polymethylpentene, amorphous nylon, polyurethane, ester base thermoplastic elastomer, styrene base thermoplastic elastomer, nylon base thermoplastic elastomer are preferable.
Moreover, polyethylene, polypropylene, ABS resin, PET, PBT or other crystalline polyesters, crystalline nylon, polyphenylene ether, polyacetal, polysulfone, polyether sulfone, polyphenylene sulfide, polyimide, polyether, polyketone, polyether ketone, polyether ether ketone, polyether nitrile, polyether imide, crystal liquid polymer, fluorine resin or other semitransparent of slightly colored resins are also accepted. In addition, silicone resin, epoxy resin, phenol resin, unsaturated polyester, diallyl phthalate, acrylic base resin, urethane resin or other publicly known thermosetting, photo-curing, moisture curing, hygrosetting liquid resins can also be used.
Using these resins, the key top of the present invention is composed of a mechanical mold key top, or a key top whose surface is integrated with a resin film, or a key top hardened by dripping and reacting liquid resin, or the like.
The key top made of resin of the present invention may have a push-button structure by attaching by means of glue or double-faced tape to a key pad including an operation section and a non-operation section formed from synthetic rubbers such as silicone rubber or ethylenepropylene base rubber, that are rubber like elastic element, or thermoplastic elastomers.
Further, the key top made of rubber like elastic element of the present invention, is a key top formed of synthetic rubber or thermoplastic elastomer. Though the composition, nature, elasticity or color tone of rubber like element used for the key top are not specially specified, it is preferable that their translucency is good, and, for instance, synthetic rubbers include silicone rubber, ethylene propylene base rubber, urethane rubber or the like, while thermoplastic elastomers include styrene base, olefin base, urethane base, ester base and PVC base elastomers.
Besides, the present invention provides for the stabilization physically and chemically of the liquid crystalline organic polymer layer, by forming on the liquid crystalline organic polymer layer on the key top, a polymer protective layer of 5 xcexcm to 60 xcexcm in thickness, by laminating and hardening non hardened liquid resin.
Though the nature, application and hardening method of liquid resin are not specified, a polymer protective layer of 5 xcexcm to 60 xcexcm can be formed, by using thermosetting type, photo-curing type or moisture curing type acrylic base, urethane base, silicone base, epoxy base, ester base or other monomer or oligomer, and laminating and hardening by application, various printing, potting or other method. If the film thickness is less than 5 xcexcm, the mechanical characteristics of the polymer protective layer is week and unable to protect sufficiently, and, on the other hand, if it is superior to 60 xcexcm, the clearness of the rainbow-colored gloss is weakened, deteriorating its beautiful appearance. More preferably, the thickness of the polymer protective film is in the range of 10 xcexcm to 40 xcexcm. In addition, a plurality of polymer protective films can be laminated.
This polymer protective layer may be colorless and transparent, the use of those colored in red, blue or yellow and translucent can further create the color tone variation of the liquid crystalline organic polymer layer.
The key top manufacturing method of the present invention includes key tops formed by filling a cavity, using a dies of desired key top shape, with heat melted thermoplastic or liquid non hardened resin by injection molding, compression molding, transfer molding, rotation molding or the like and hardening the same, or key tops formed into a key top shape by printing character, symbol or the like on a resin film, placing the same in a mold cavity, and injecting heat melted resin into the cavity, or key tops molded by applying non hardened liquid resin on a key pad made of rubber like elastic element, or on a polyester, polyamide, polyurethane or other films or a substrate made of sheet polymer material and hardening.
The method of applying a liquid resin, potting system, dispenser system, pad printing system or other transfer system, dipping system, or the like is further described herein.